Routing is an inherent problem with long distance telephone calls. Accordingly, there are many systems for selecting routes between long distance stations. It is possible for example to go from New York to Los Angeles through Chicago or through Dallas, Tex., both with almost equal facility and speed even though some routes are longer than others. Now in addition to selecting a particular route, it is also useful to be able to select from between different methods of traversing the long distances. For example, it is possible to route a call through the Bell System long lines. It is also possible to route the call through alternate carriers such as MCI and Sprint, for example. Thus, with modern technology, it is possible to use one system in favor of another system to minimize the cost. Such savings in long distance calls could easily add up to large sums of money for businesses which customarily make many long distance calls. Thus it is important to provide an efficient routing system wherein the cost of the call to the caller is a determining factor.
In addition to routing the calls through the least costly routes, it is also important to speedily determine when the called party answers to determine the exact time of the telephone call, that is the time for which the charged customer has to pay. Such a determination is especially useful in PABX systems used in hotels and motels. For example, when a guest originates a call in a hotel or a motel he is not usually interested in how the call gets from his telephone to the called party's telephone. He is of course interested in the cost of such a call and since this appears on his bill he can readily check the cost. Oftentimes the guest makes calls just prior to departure. In such cases it is necessary for the hotel or the motel to know the cost of the call accurately so as to be able to bill the guest and not suffer any losses.
As a matter of fact, with an efficient system for selecting the least expensive route and for accurately determining the cost of the call, it is possible for the hotel or the motel to charge the guest less than he would normally pay for the call through Bell long lines and still make a profit per call where routed through alternate carriers.
Presently, however, there is no way that the hotel or the motel can accurately determine the length of the call because of lack of answer supervision from the central office. In present call routing systems, the call is timed from a fixed period of time after its initiation until its termination. For example, call routing systems assume that if a hotel guest is off hook for a period of say 30 seconds or more, the call was answered while in fact the line could have been left ringing for more than 30 seconds. The guest would in such instances be charged for calls which were not answered. In the proposed system, both the initiation of the call and the termination are readily detected and thus the time span therebetween is readily measured. Therefore, there is a longfelt need for a private system such as PABX'x, PABX add-ons, or even a system within a subscriber station that can accurately determine when the called party answers in addition to when the call is terminated.